1. Field of the Invention:
This invention relates to an electrostatic recording apparatus which can accomplish drawing a fixing device, separation of a pressing roller from a fixing roller and separation of a transfer portion from an image retainer.
2. Description of the Prior Art:
Electrostatic recording apparatuses are extensively used as electronic reproducing machines, laser printers, LED printers and the like. An example of an electronic reproducing machine, namely, a reproducing apparatus, will be described hereinafter.
In the reproducing apparatus, a light from a light source is exposed to the original surface on a document glass plate, a reflected light from the original surface is illuminated on a photosensitive drum through a reflecting mirror to form an electrostatic latent image, which is developed by a developing portion, a toner image is then transferred onto a recording paper supplied timely, charge elimination and/or separation is effected and thereafter the recording paper is ejected through a fixing device. The transfer portion and the photosensitive drum, and the fixing roller within the fixing portion and the press roller used in such a reproducing apparatus as described may be released in pressure in order to facilitate a removal of a recording paper possibly jammed during a passage thereof. In the case of conventional reproducing apparatuses, a separation mechanism between the transfer portion and the photosensitive drum, for example, a separation mechanism between the photosensitive drum and a transporting portion is disclosed, for example, in Japanese Patent Application Laid-Open Nos. 77733/1977, 75444/1977 and 92745/1979 and Japanese Utility Model Application Laid-Open No. 108451/1980, according to which releasing mechanisms for the fixing roller within the fixing device and the pressing roller are separately provided, and therefore, the operation thereof was cumbersome and in addition, it was not possible to secure a large space used to clear the jamming.
Furthermore, a conventional fixing device of this kind has a handle adapted to move a fixing unit from a given position to a pull-out position and vice versa, and a lock-releasing lever for releasing a pawl provided to lock the fixing unit at the given position. Accordingly, when the fixing unit is moved from the given position to the pull-out position, two actions are needed, one for operating the lock releasing lever to disengage the pawl and the other for operating the handle, which leads to not only cumbersome in operation but also, in case of the aforesaid pawl, a certain play essentially required in a locking portion of the fixing unit where the pawl is locked in order to turn the pawl in a releasing direction, with the result that the fixing unit cannot be firmly secured to the given position and the position thereof becomes unstable, thus involving a problem that a deviation of transfer or the like is created.
Moreover, the fixing device for fixing a toner image transferred onto a recording paper normally comprises a pair of upper and lower press rollers, whereby a toner is molten by the pressure of the press rollers and heat applied to the rollers to fix the image. Therefore, the recording paper is apt to be jammed during such operation and a contamination of toner is liable to adhere. In view of the foregoing, the fixing unit is designed so that it may be pulled out in the ejecting direction of the recording paper to facilitate the operations such as the handling of jam, the cleaning of rollers and the like.
However, in the past, the pressing and releasing of the press rollers within the fixing unit have been done by a mechanism separately from the pull-out mechanism of the fixing unit, thus resulting in troublesome in operation.
In addition, the fixing device of an electrophotographic reproducing machine is interiorly provided with a fixing roller driven by a drive gear supported on the frame of the reproducing machine, and normally the shaft of the fixing roller has to be positively secured at a position where it is driven in such a manner that the aforesaid shaft is parallel to the shaft of the photosensitive drum in order to prevent occurrence of fixing creases and a deviation in position. Furthermore, in the event that jamming should occur, it would have to be moved temporarily from the fixing position. That is, it is desired that the fixing device be positively secured so that it may not be moved even if the fixing roller is driven by a drive gear and the fixing device may be easily unlocked.